12 titles recommended if you like Requiem of the Rose King
Aoi Bungaku Series
Sacrificial Princess and the King of Beasts
Berserk
Tokyo Ghoul
The Seven Deadly Sins: Four Knights of the Apocalypse
Parasyte -the maxim-
Hell Girl
Basilisk
Seraph of the End
The Ancient Magus' Bride
Fullmetal Alchemist: Brotherhood
Bye Bye, Earth